Method and system for the remediation of aquatic facilities

ABSTRACT

A system and method for controlling the accelerated remediation of the water of an aquatic facility using at least one sanitizer sensor, a pH sensor, a temperature sensor and a chlorine dioxide sensor all interfaced with a programmable controller that is programmed to implement a remediation cycle and configured to calculate a Ct value of the water chemical feed system. The programmable controller activates a chemical feed system to supply an acid, an oxidizer and a chlorite ion donor to a conduit to form chlorine dioxide that is supplied to the water until a desire Ct value is reached.

FIELD OF INVENTION

The invention relates to a method and system for accelerated remediation of the water of an aqueous system, such as an aquatic facility, using a programmable controller programmed to implement a remediation cycle that accelerates the in-situ generation of chlorine dioxide and configured to calculate a Ct value, track the Ct value in real-time and continue the remediation until a target Ct value is achieved.

BACKGROUND

Free chlorine and free bromine are common sanitizers for the treatment of aquatic facilities. While effective at controlling bacteria counts in the water, they have limited efficacy against waterborne pathogens that are resistant to the sanitizers such as Cryptosporidium.

The Centers for Disease Control and Prevention has reported waterborne pathogens such as Cryptosporidium are accountable for nearly 80% of all Recreational Water Illness (RWI) in the United States. To a lesser degree but still significant are other waterborne pathogens such as Legionella that are resistant to chlorine due to the formation of biofilm that protect the bacteria from the chlorine.

Chlorine dioxide is favored over many oxidizing biocides due to its biocide efficacy over a broad pH range, low use rate, biofilm penetration and high selectivity in contaminated water.

In order to ensure aquatic facilities are properly protected from waterborne pathogens, there is a need for controlling two types of applications used for remediating. The first is a daily remediation and the second is a rapid recovery shock.

Daily remediation is necessary due to the fact that aquatic facilities that have been compromised by a waterborne pathogen such as Cryptosporidium will not know they have been compromised until symptoms are identified and confirmed often many days or even weeks later. By the time confirmation is made, the pathogen can spread to hundreds or even thousands of people who used the aquatic facility and/or have spread the pathogen to other aquatic facilities thereby propagating the spread of infection. Implementing an automated system that remediates the aquatic facility on a daily basis would dramatically reduce the potential for infection as well as virtually eliminate the spread to other aquatic facilities.

Rapid recovery shock is applied when a known event such as a fecal release is identified. The control system can be manually activated to implement a remediation cycle, track the Ct value in near real-time, and terminate the remediation cycle when the targeted Ct value has been achieved. Furthermore, the control system can then be programmed to neutralize excess treatment (e.g. chlorine dioxide and/or excess sanitizer) after achieving the target Ct value to prepare the aquatic facility for opening to the public.

U.S. Pat. Nos. 7,922,933, 7,927,509, and 7,976,725 which are herein incorporated by reference in their entirety, disclose a cyclic process for the in-situ generation of chlorine dioxide. The cyclic process utilizes bromide ions that are activated by an oxidant to produce free bromine. The free bromine oxidizes chlorite ions producing chlorine dioxide. Chlorine dioxide inactivates microbiological organisms (i.e. Cryptosporidium). During this process the free bromine and at least some portion of the chlorine dioxide are reduced back to bromide ions and chlorite ions respectively which are recycled back to free bromine and chlorine dioxide utilizing the cyclic process.

My earlier U.S. Published Patent Application Nos. 2019-0300398 and 2020-0346948, which are herein incorporated by reference in their entirety, disclose methods for in-situ generation and stabilization of chlorine dioxide in the water of an aquatic facility using UV activation of chlorite ions.

My earlier U.S. Published Patent Application Nos. 2021-0323838 and 2022-0127164, which are herein incorporated by reference in their entirety, disclose methods for in-situ generation and stabilization of chlorine dioxide in the water of an aquatic facility.

There is a need for an improved method of generating chlorine dioxide to remediate the water of an aquatic facility without the use of bromine.

SUMMARY OF THE INVENTION

Objectives of the invention include mitigating over 80% of all Recreational Water Illness (RWI) as described by the Centers for Disease Control and Prevention, without the use of bromine.

The objectives of the invention and other objectives can be obtained by a first embodiment which comprises a method for accelerating remediation of a main body of water in an aquatic facility, the method comprising:

calculating a Ct value of the water by a programmable controller;

activating chemical feed systems by the programmable controller so that the chemical feed systems deliver an acid, an oxidizer and a chlorite ion donor to a conduit in communication with the water;

allowing the acid, the oxidizer and chlorite ion donor to react in the conduit and form chlorine dioxide; and

supplying the chlorine dioxide from the conduit to the water; and

sustaining a concentration of chlorine dioxide in the water until a targeted Ct value of the water is reached to achieve remediation of the water.

The objectives of the invention and other objectives can be obtained by a second embodiment which comprises a system for controlling the accelerated remediation of a main body of water in an aquatic facility, the system comprising:

at least one sanitizer sensor for measuring a concentration of sanitizer in the water;

a pH sensor for measuring a pH of the water;

a temperature sensor for measuring a temperature of the water;

a chlorine dioxide sensor for measuring the concentration of chlorine dioxide in the water;

chemical feed systems for supplying an acid, an oxidizer and a chlorite ion donor to a conduit connected to the water;

a programmable controller in communication with the sanitizer sensor, the pH sensor, the temperature sensor, the chlorine dioxide sensor, and the chemical feed systems;

the programmable controller is programmed to implement an accelerated remediation cycle by activating the chemical feed systems to achieve localized high concentrations of the acid, the oxidizer and the chlorite ion donor which react to form chlorine dioxide in the conduit that is supplied to the water;

the programmable controller is programmed to record a chlorine dioxide concentration measured by the chlorine dioxide sensor;

the programmable controller is programmed to calculate a Ct value of the water; and

the programmable controller is programmed to sustain a concentration of chlorine dioxide in the water until a targeted Ct value is reached to achieve remediation.

The system in accordance with the second embodiment further comprises the programmable controller terminating the remediation cycle by applying reducing agent to neutralize excess chlorine dioxide and sanitizer in the water.

The programmable controller calculates, records, and stores the Ct value of the water. The programmable controller can also display the Ct value. The programmable controller can be programmed to forecast the time to achieve the desired Ct value of the water. The calculated Ct value can be based on the rolling average of the chlorine dioxide concentration. The Ct value is calculated at any desired interval, for example every 0.1 to 60 minutes. The Ct value can be calculated by:

Ct value=[(ΣX _(n))÷n]×T

Where:

-   -   “X” is the chlorine dioxide concentration in mg/l (or ppm).     -   “n” is the number of chlorine dioxide values recorded over a         period of time since beginning the remediation cycle.     -   “T” is the period of time (minutes) that has lapsed since         beginning the remediation cycle.

Any suitable sanitizer sensor can be utilized, such as an ORP sensor or an amperometric sensor. The system preferably utilizes both ORP and amperometric sensors.

The implementation of the accelerated remediation cycle can be initiated automatically or manually, as desired. The programmable controller can be programmed to terminate the remediation cycle at a desired time.

Chlorine dioxide is produced within the conduit. When the accelerated remediation cycle is initiated by the programmable controller, the controller activates the chemical feed systems to achieve localized high concentrations of chemicals in the conduit. The localized high concentration of chemicals react to produce high concentrations of chlorine dioxide in the conduit.

The chemicals comprise a source of free chorine, and acid source and a chlorite source. The concentration of free chlorine (as Cl₂) and chlorite (as ClO₂ ⁻) are in a molar ratio of between 0.5:2 to 3:2, more preferred 0.75:2 to 2.5:2 and most preferred 1:2 to 2:2 respectively.

The acid should be applied at a sufficient concentration to achieve a pH in the conduit of between 2 to 6.5, more preferably 3 to 6 and most preferred 3.5 to 5.5. A pH sensor can optionally be inserted into the conduit downstream of the acid feed point and be interfaced with the programmable controller. The programmable controller can then adjust the feed rate of acid to achieve a targeted pH.

The molar ratio of chlorine to chlorite and pH can be optimized based on the lapsed time between the location of chemical feed to the time the water in the conduit is injected into the pool. The longer the lapsed time the more reaction time there is to in-situ generate chlorine dioxide. In the case of shorter lapsed time periods, it may be advantageous to apply a higher molar ratio of chlorine to chlorite and lower the pH to below 5.5 to maximizes the concentration of hypochlorous acid thereby increasing the rate of reaction and subsequent formation of chlorine dioxide.

Optimizing the molar ratio of chlorine to chlorite and pH has demonstrated the ability to achieve a conversion of chlorite to chlorine dioxide of ≥70%, more preferred ≥80% and most preferred ≥90% conversion. The demonstrated ability to achieve high conversion of chlorite to chlorine dioxide in dilute solutions achieved within the conduit of the circulating system of a swimming pool provides a means of remediating the swimming pool safely and cost effectively without the need for costly and potentially dangerous chlorine dioxide generators.

By producing high concentrations of in-situ generated chlorine dioxide within the conduit, the process can be carried out safely without the need for expensive or potentially dangerous chlorine dioxide generators. Furthermore, as illustrated in FIG. 11, the remediation cycle is accelerated due to the rapid buildup of chlorine dioxide in the water. The rapid buildup of chlorine dioxide results in a reduction in the time required to achieve the target Ct value thereby accelerating the remediation cycle.

The system can further comprise neutralizing excess chlorine dioxide and/or neutralizing excess sanitizer and/or oxidizer by applying a reducing agent to the water from a reducing agent feed system.

The programmable controller can be programmed to evaluate previous remediation cycles to determine the required application rate of chlorine dioxide to forecast future remediation cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the chlorine dioxide concentration and calculated Ct Value (min×mg/l) for a daily remediation (test #1) using the cyclic process for the in-situ generation of chlorine dioxide.

FIG. 2 illustrates the events log for test #1 using ORP as the means for controlling the feed of chlorine. Note with the addition of Cryptolyte® (sodium chlorite) caused the ORP to drop resulting in the feed of chlorine. The chlorine concentration elevated as a result. As the cyclic process depleted the chlorite, the ORP gradually increased.

FIG. 3 illustrates the chlorine dioxide concentration and calculated Ct Value (min×mg/l) for a daily remediation (test #2) using the cyclic process for the in-situ generation of chlorine dioxide. In this test, the chlorine concentration remained stable illustrating what occurs when the control system is converted to amperometric control of the chlorine feed.

FIG. 4 illustrates the free chlorine in test #2 measured using an amperometric sensor remained relatively constant during the remediation process.

FIG. 5 illustrates test #3 which represented a Rapid Recovery Shock during daytime hours. This treatment method exemplifies the method employed to recover an aquatic facility quickly after a known event such as a fecal release.

FIG. 6 illustrates the events that took place during test #3.

FIG. 7 illustrates the Ct values (min×mg/l) for achieving various log reductions in viable Cryptosporidium using the cyclic process. The method employed represents a Rapid Recovery Shock.

FIG. 8 illustrates the Ct values (min×mg/l) for achieving various log reductions in viable Cryptosporidium using the cyclic process. The method employed represents a Daily Remediation.

FIG. 9 illustrates the reactions within the conduit resulting in in-situ generation of chlorine dioxide.

FIG. 10 illustrates a remediation system for remediating the water of an aquatic facility.

FIG. 11 illustrates the accelerated remediation cycle resulting from the in-situ generation of chlorine dioxide resulting from localized high concentrations of oxidizer, chlorite ions and in this example acid in the conduit using the cyclic process.

FIG. 12 is a graph illustrating the concentration of chlorine dioxide during the remediation process.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be explained with reference to attached non-limiting Figs. FIG. 10 illustrates an exemplary remediation system 2 for remediation of the water 4 in an aquatic facility. In an aquatic facility, the water 4, such as in a swimming pool, typically flows out of the pool through exit conduit 32 to a surge tank 6, water pump 18, filter 20, heater 22, and then back into the pool via return conduit 33. A chemical feed system 40 is connected to the water 2, such as through the conduit 32. Examples of chemical feed systems 40 include a oxidizer feed system 30 for supplying sanitizer and oxidizer to the water 4, an acid feed system 28 for supplying chemicals to adjust or control the pH of the water 4, a chlorite ion donor feed system 26 for supplying chlorite ions to the water 4, and an optional reducing agent feed system 38 for supplying a reducing agent or other chemicals to the water 4.

A first sanitizer sensor 8 and a second sanitizer sensor 10 can be used measure the concentration of sanitizer in the water 4. For example, the first sanitizer sensor 8 can be an ORP senor and the second sanitizer sensor 10 can be amperometric type sensor. A pH sensor 12 can be used to measure the pH of the water 4. A chlorine dioxide sensor 14 can be used to measure the concentration of chlorine dioxide in the water 4. A temperature sensor 16 can be used to measure the temperature of the water 4. A flow sensor 17 can be used to measure the water flow through the conduit 36 from which the sensors 8, 10, 12, 14, 16 and 17 are connected to sample the water 4.

A programmable controller 24 is used to control the system 4. The remediation feed system 26, the acid feed system 28 and the oxidizer/sanitizer feed system 30 can be connected to and controlled by the programmable controller 24. The sensors 8, 10, 12, 14, 16 and 17 can be connected to and controlled by the programmable controller 24.

The Florida Department of Health pH range for the water 4 of an aquatic facility is from 7.2 to 7.8 with the recommended range being 7.4 to 7.6. During a remediation cycle, the programmable controller 24 automatically monitors and controls the pH to operate within these ranges using the pH sensor 12 and acid feed system 28. Due to the significant lag time between the time of feeding pH related chemicals (i.e. acid) from the acid feed system 28 and the time to return a representative sample for the pH sensor 12 to measure, control logic is used to minimize the potential for overfeed of the chemical. One example of control logic is time-proportioned control.

The Florida Department of Health Sanitizer range for chlorine (reported as Cl₂) sanitizer is from 1-10 ppm in pools and 2-10 ppm in spas. For bromine (reported as Br₂) the ranges is 1.5-10 ppm in pools and 3-10 ppm in spas. During a daily remediation cycle the programmable controller will automatically control the feed of sanitizer within these ranges using the first and second sanitizer sensors 8 and 10 and sanitizer feed system 30. However, during a rapid recovery shock, the range of chlorine will be 1-50 ppm as Cl₂ in the case of chlorine and 2-100 ppm as Br₂.

During the remediation cycle the chlorine dioxide concentration, measured by the chlorine dioxide sensor 14, can vary based on the type of remediation. For a daily remediation cycle, the chlorine dioxide concentration can range from 0.0 to 2.0 ppm as ClO₂. When the remediation cycle begins, the chlorine dioxide concentration at Time=0 is 0.0 ppm. Over time the concentration of chlorine dioxide will increase. The desired maximum concentration is dependent on the time constraints to achieve the desired Ct value. When longer times are permitted such as in the case of an evening remediation when the aquatic facility is closed to the public, the maximum concentration of chlorine dioxide maybe as low as 0.1 ppm as ClO₂. In the event of a rapid recovery shock, it may be more desirable to increase to maximum concentration in the water as high as 20 ppm as ClO₂ to minimize the time the aquatic facility is closed to the public. Regardless of the range or maximum concentration of chlorine dioxide achieved, as long as the desired Ct value is achieved then remediation has been achieved.

The Ct value (min×mg/l) can range from 1-200, more preferred 2-180, and most preferred 5-160. The optimum Ct value will depend on what is being remediated and the method of remediation being used. Referring to FIGS. 7 and 8, the charts illustrate the log reduction for Cryptosporidium for various Ct values using the cyclic process. Depending on the method used the Ct value required to remediate the Cryptosporidium (3-log reduction) varied. In the case of penetrating and removing biofilm in the piping of an aquatic facility the Ct value may be higher depending on the thickness and surface area covered by the biofilm.

The programmable controller 24 tracks the chlorine dioxide concentration measured by the chlorine dioxide sensor 14 during the remediation cycle and calculates the rolling average (also referred to as a “moving average”). The rolling average is multiplied by the time that has lapsed measured in minutes to update the Ct value in real-time. The rolling average can be updated over any desired period of lapsed time. One preferred period of lapsed time ranges from 0.1 to 60 minutes, more preferred 0.2 to 30 minutes, and most preferred 0.5 to 10 minutes. The ability to frequently update the real-time Ct value allows the programmable controller to forecast the trend and project when the targeted Ct value will be reached.

The ability to forecast when a remediation will be achieved, the programmable controller 24 can be programmed to learn from the previous remediation cycles and project and/or automatically adjust the concentration of chlorine dioxide and/or the application rate of chlorine dioxide in future remediation cycles to achieve a targeted Ct value within a desired time interval. For example, when using time-proportioned control logic, the controller 24 alters the feed duration of chlorine dioxide from the remediation feed system 26 based on how far the measured concentration of chlorine dioxide measured by the sensor 14 is from the set-point. If the sun's UV for example decomposes the chlorine dioxide at a high rate, the time required to achieve Ct value can be substantially increased. By evaluating the number of feed cycles, duration of the feed cycles, and the deviations from the set-point during and after said feed cycles, corrections can be made to compensate for the losses in chlorine dioxide concentration as well as the lag-times between applying chlorine dioxide and observing (measuring) the result.

The remediation cycle can comprise a single application of chlorine dioxide. For example, referring to FIGS. 1 and 2 illustrate that a single application of sodium chlorite under the brand name Cryptolyte® provided sufficient chlorine dioxide using the cyclic process to achieve a 3-log reduction in Cryptosporidium in only 7 hours. The remediation cycle began with the feed of Cryptolyte® at 8:00 μm and by 3:00 am the remediation cycle had achieved a Ct value of 66 (min×mg/l). Referring to FIG. 8, a Ct value of 66 (min×mg/l) is sufficient to remediate Cryptosporidium.

The remediation cycle may also apply multiple applications of chlorine dioxide. For example, when the remediation cycle is initiated the programmable controller 24 can control the concentration of chlorine dioxide by applying multiple applications of chlorine dioxide to sustain a predetermined set-point of chlorine dioxide. The programmable controller 24 an apply an initial application of chlorine dioxide at a predetermine concentration, then implement periods of additional applications of chlorine dioxide to target a predetermined set-point. Control logic can be used to compensate for lag-time between application of treatment and detection of the applied treatment. Time-based proportional control provides a method of compensating for the lag-time.

The remediation cycle can be automatically initiated by the programmable controller 24 such as in the case of planned evening remediation when the aquatic facility is closed to the public. However, in the case of a fecal release, the remediation cycles can be initiated manually, then carry out the functions automatically to perform the remediation.

The programmable controller 24 can be configured to calculate, record, and store the Ct value. Optionally the controller 24 can display the Ct value on the display 25 and callout to a technician in the event of a successful or failed remediation cycle. Once the Ct value has been achieved, the controller 24 terminates the remediation cycle.

The accelerated remediation cycle can be automatically initiated by the programmable controller 24 such as in the case of planned evening remediation when the aquatic facility is closed to the public. However, in the case of a fecal release, the accelerated remediation cycle can be initiated manually, then carry out the functions automatically to perform the accelerated remediation. An accelerated remediation cycle can be implemented by the programmable controller activating simultaneously the chlorite ion donor feed system 26, oxidizer feed system 30 and acid feed system 28. Acid is typically desired to accelerate the rate of reaction by lowering the pH favoring the formation of hypochlorous acid, however if a separate acid based oxidizer exemplified by potassium monopersulfate or electrolysis of chloride salts is used, acid may not be required or may be significantly reduced. The simultaneous chemical feeds achieve localized high concentrations in the conduit. Fluid dynamics within the conduit combine the high concentrations of chemicals to induce a high rate of reaction resulting in elevated concentrations of chlorine dioxide in the conduit. The ability to rapidly increase the concentration of chlorine dioxide in the water of the aquatic facility accelerates the completion of the remediation cycle. The optimization of acid feed may be further improved by implementing a pH sensor into the conduit 42 that is in fluid contact with the programmable controller that can automatically adjust the acid feed 28.

When a targeted Ct value is achieved and the remediation cycle is terminated, adjustments to the water 4—chemistry may be required before opening the aquatic facility to patrons. In some cases such as a rapid recovery shock, excess sanitizer and chlorine dioxide can make the water unsuitable to swimmers. Neutralizing the excess sanitizer and chlorine dioxide can be automated by the system. The amperometric sensor 10 measures the excess chlorine as well as chlorine dioxide. The chlorine dioxide sensor 14 measures specifically chlorine dioxide. The difference between the two sensors 10 and 14 provides a relative concentration of sanitizer.

A reducing feed system 38 interfaced with the programmable controller 24 and in fluid contact with the water 4 of the aquatic facility provides the ability to feed a reducing agent exemplified by sodium thiosulfate in order to neutralize the excess oxidizers (sanitizer etc.), or any other desired chemicals. Furthermore, knowing the strength of the sodium thiosulfate solution, the feed rate of the chemical feed system 40, the volume of water to be treated etc., the programmable controller 24 can be programmed to calculate how much reducing agent to apply, then track the reductions in excess and adjust as needed until the water meets the water chemistry requirements to open.

The following terms used throughout the specification have the following meanings unless otherwise indicated.

“A” or “an” means “at least one” or “one or more” unless otherwise indicated.

“Comprise”, “have”, “include” and “contain” (and their variants) are open-ended linking verbs and allow the addition of other elements when used in a claim. “Consisting of” is closed, and excludes all additional elements.

“Consisting essentially of” excludes additional material elements, but allows the inclusions of non-material elements that do not substantially change the nature of the invention.

As used herein, the term “aquatic facility” is used with reference to all structural components and equipment comprising an aqueous system used by humans for exercise, sports and/or recreation. Examples of aquatic facilities include but are not limited to: residential swimming pools, water parks, theme parks, swimming pools, spas, therapy pools, hot tubs and the like.

As used herein, the term “aqueous system” describes a body of water 4 that can be treated using the disclosed composition. Examples of aqueous systems include recreational water, cooling towers, cooling ponds and wastewater.

As used herein, “recreational water” is water 4 used by mammals (i.e. humans) for various activities such as swimming, exercise, water sports, recreation, physical therapy and diving. Examples of aqueous systems comprising recreational water include: swimming pools, hot tubs, feature pools, spas, water-park rides, therapy pools, diving wells etc.

As used herein the term “Ct value” is defined as the product of the average concentration of an oxidant (mg/l) and time (minutes) of exposure to the oxidant. For example, if the average chlorine dioxide concentration of ClO₂ is determined to be 2.2 mg/l over a 20 minute period of time, the Ct value is calculated by multiplying the average concentration of chlorine dioxide by the time.

Ct value=2.2 mg/l×20 min

Ct value=44(min×mg/l)

The Ct value can be targeted based on laboratory and/or field studies to achieve the desired level of inactivation. Comparatively, low Ct values (i.e. Ct=1 mg·min/l) may achieve a 6-log reduction in bacteria like E. coli, while higher Ct values (i.e. Ct=90 mg·min/l) may be required to reduce a parasite like Cryptosporidium by 3-log.

As used herein, “algorithm to calculate the Ct value” describes a mathematical equation for calculating the Ct value in near real-time. One example of a suitable algorithm for calculating the Ct value follows:

Ct value=[(ΣX _(n))÷n]×T

Where:

“X” is the chlorine dioxide concentration in mg/l (or ppm). “n” is the number of chlorine dioxide values recorded over a period of time since beginning the remediation cycle. “T” is the period of time (minutes) that has lapsed since beginning the remediation cycle.

The algorithm calculates the Ct value over the period of the remediation cycle. The algorithm calculates the sum of all the chlorine dioxide values recorded. The sum is divided by the number of chlorine dioxide values to obtain the average chlorine dioxide concentration. The average chlorine dioxide concentration is then multiplied by the lapsed time (minutes) to calculate the Ct value (mg/l×min). The Ct value is updated in real-time by calculating the rolling average of the chlorine dioxide concentration, then multiplying the rolling average by the lapsed time (minutes) since beginning the remediation cycle.

As used herein, “rolling average” is the average chlorine dioxide concentration resulting from the accumulated chlorine dioxide concentrations (mg/l) divided by the number of chlorine dioxide measurements by the chlorine dioxide sensor 14 and recorded. The rolling average is used to provide a real-time Ct value by multiplying the rolling average by the remediation cycle's lapsed time (i.e. number of minutes since beginning the remediation cycle). The rolling average can be updated over any desired period of lapsed time. One preferred period of lapsed time ranges from 0.1 to 60 minutes, more preferred 0.2 to 30 minutes, and most preferred 0.5 to 10 minutes.

As used herein, the term “remediation cycle” describes the process of introducing chlorine dioxide into the water of an aquatic facility at a concentration sufficient to achieve a targeted Ct value (min×mg/l). The chlorine dioxide can be introduced to the water 4 from the remediation feed system 26 using ex-situ and/or in-situ methods. An ex-situ method may comprise a chlorine dioxide generator as part of the remediation feed system 26. An in-situ method may comprise the cyclic process and/or UV activation of chlorite as part of the remediation feed system 26. The ex-situ method can be coupled with the in-situ method to accelerate the concentration of chlorine dioxide using a chlorine dioxide generator as well as maximize efficiency using the cyclic process.

As used herein, “accelerated remediation” describes the ability to reduce the time required to achieve the target Ct value for remediation by increasing the concentration of chlorine dioxide in the water of an aquatic facility while applying an amount of chlorite ion donor equal to or less than the amount used during a remediation cycle using the cyclic process for the in-situ generation of chlorine dioxide in dilute solutions. The accelerated remediation is achieved by increasing the chlorine dioxide concentration using the accelerated remediation cycle.

As used herein, “accelerated remediation cycle” describes delivering chemicals for the in-situ generation of chlorine dioxide into a conduit to achieve localized high concentrations. The localized high concentrations of chemicals interact resulting in higher concentrations of chlorine dioxide within the conduit. By accelerating the production rate of chlorine dioxide, the concentration of chlorine dioxide in the water of the aquatic facility is elevated in a short period of time when compared to in-situ generation using dilute concentrations of chemicals. The rapid elevation of chlorine dioxide in the water dramatically accelerates the remediation process by reducing the time required to achieve the targeted Ct value. The accelerated remediation cycle can be controlled by a programmable controller that activates the feed of the chemicals at essentially the same time to achieve the localized high concentrations in the conduit. The remediation cycle continues until at least the targeted (desired) Ct value is achieved.

As used herein, “localized high concentrations” refers to the concentration of chemicals used for the generation of chlorine dioxide within the conduit. The volume of water in the conduit is only a small portion of the volume of water in the swimming pool. When the said chemicals are applied to the conduit, the concentration in the conduit may be 100's of times higher than what will be achieved once the chemicals are dispersed in the large volume of water in the swimming pool. For example, a 100,000 gallon swimming pool is required to have a turnover every 6 hours or less to meet typical Dept of Health codes. A circulation rate of approximately 280 gpm is required. If the programmable controller is programmed to feed sufficient chemical to produce 5 ppm as ClO₂ based on the volume of water in the pool and the chemicals are feed over three minutes, the localized high concentrations within the conduit are sufficient to produce approximately 119 ppm as ClO₂. By utilizing the cyclic process, high conversion efficiency can be achieved without the use of a chlorine dioxide generator.

As used herein, the term “cyclic process” describes the in-situ generation of chlorine dioxide resulting from the recycling of substantially inert anions comprising bromide and chlorite into their oxyhalogen surrogates, exemplified by hypobromous acid and chlorine dioxide respectfully followed by reduction back to their respective anions, and where the process is repeated (FIG. 9). The cyclic process comprises activating bromide ions with the oxidant to produce free bromine, the free bromine oxidizes chlorite ions to produce chlorine dioxide, reducing at least some free bromine back to bromide ions and repeating the process. Chlorite ions resulting from the reduction of chlorine dioxide are also recycled back to chlorine dioxide in the cyclic process.

As used herein, the term “chlorite ion donor” and “chlorite donor” is a compound that comprises an alkali metal salt comprising chlorite anions ClO₂ ⁻, chlorine dioxide, or any convenient direct or indirect source of chlorite anions. For example, chlorine dioxide can indirectly produce chlorite due to reduction in an aqueous system. Sodium chlorite directly supplies chlorite anions.

As used herein, the term “chlorite ion” and “chlorite anion” (also referred to as “chlorite”) comprises chlorite having the general formula ClO₂ ⁻. The chlorite is the anion released when sodium chlorite is dissolved in water and converts to chlorine dioxide.

As used herein, the term “recycled” means at least some portion of the recovered bromide ions and chlorite ions are regenerated to their respective oxyhalogen compounds, followed by reduction back to their respective anions, and where the process is repeated.

As used herein, the term “Cryptosporidium” is used to represent any form of parasitic microbiological organism from the family of Cryptosporidium. An example of Cryptosporidium is Cryptosporidium parvum (also referred to as C. parvum, C. parvum and Cryptosporidium parvum). Other examples of Cryptosporidium include but are not limited to: C. hominis, C. canis, C. felis, C. meleagridis, and C. muris. It is to be noted that inclusion or exclusion of italic characters or print when referring to Cryptosporidium or any of its many variants does not in any way detract from its intended descriptive meaning.

As used herein, the term “microbiological organisms” is used with reference to all forms of microbiological life including: parasites, bacteria, viruses, algae, fungus, and organisms encased in biofilms.

As used herein, “parasites” includes any species of organism including Cryptosporidium, Giardia and Ameba that can be transferred to humans by water and cause waterborne parasitic disease in humans.

As used herein, the term “inactivation” is used with reference to the ability to deactivate, kill, or destroy microbiological organisms.

As used herein, “remediation” is defined as the ability to reduce the level of waterborne pathogens and/or algae to levels at or below that deemed acceptable by various regulatory agencies exemplified by State and local Departments of Health, U.S. Environmental Protection Agency, and/or the Centers for Disease Control and Prevention. Examples of achieving remediation comprise at least one of the following: less than 1 CFU per ml of viable bacteria determined by heterotrophic plate count; greater than or equal to a 3-log reduction of parasites, and/or rendering the aqueous system free of algae.

As used herein, “programmable controller” 24 describes a control system comprising at least a microprocessor and/or programmable logic controllers (PLC) with relays and interfaces with sensors and chemical feed systems. The operations described herein can be implemented as executable code stored on a computer or machine readable non-transitory tangible storage medium in communication with the microprocessor.

Non-limiting examples of how the programmable controller 24 can be used to control chemical feed systems 40 includes: actuating chemical feed; varying the rate of chemical feed; energizing an electronic device such as a chemical feed pump, solenoid valve; stopping chemical feed; and initiating a neutralization cycle that removes residual chemicals from the water using neutralizing chemicals exemplified by sodium sulfite. The programmable controller 24 receives inputs either manually and/or automatically from sensors exemplified by the non-limiting examples: pH sensor 12, ORP sensor 8, amperometric sensor 10, chlorine dioxide sensor 14, temperature sensor 16, flow sensor 17, flow switch and the like.

The programmable controller 24 uses some form of control logic to control and optimize the feed of chemicals. Examples of control logic include: time-proportional, proportional, derivative, integral, proportional-integral-derivative control.

As used herein, “fluid contact” describes contact between conduits 32, 33 capable of transporting liquid to and from the main body of water (i.e. swimming pool) 4 at the aquatic facility. Specifically regarding aquatic facilities, sensors and chemical feed systems 40 are in fluid contact with the water 4 of an aquatic facility in or near the mechanical room where water is recovered from the pool, filtered 20, sometime heated 22 and returned to the pool. The piping (conduit) 36 transporting the water supplies water for the sensors to monitor the various parameters such as pH 12, sanitizer concentration 8, 10, temperature 16 and chlorine dioxide 14. Chemical feed 40 is generally applied into the return piping 33 after being filtered and where applicable heated to prevent corrosion of the heater 22.

As used herein, “chemical feed systems” 40 describe any convenient device that is fluid contact with both the chemicals and the water of the aquatic facility. The chemical feed systems 40 can be controlled to deliver the desired amount of chemicals exemplified by the non-limiting examples chlorine, acid such as HCl or CO₂ and sodium chlorite. Non-limiting examples of chemical feed systems include: chemical metering pumps, educators, modulating control valves and the like.

As used herein, “flow sensor” 17 describes a device that can detect a liquid flowing through a pipe or conduit 36. The flow sensor 17 can be a flow transmitter that measures the flow rate, but is not required to measure the flow rate. The flow sensor 17 detects motive water in the pipe or conduit 36. One non-limiting example of a flow sensor that does not measure the flow rate is a Rotorflow® Flow Sensor available by Gems™ Sensors and Controls.

As used herein, “energize” and “energizing” and its variations describes the activation of an electrical device by closing a circuit that delivers an electrical current to the electrical device so that the electrical device performs a desired function. For example, a flow sensor detects motive water followed by the control panel energizing the chemical feed systems. In contrast, when motive water is no longer confirmed by the flow sensor, the control panel stops the chemical feed systems.

As used herein, “actuated” and “actuating” and its variations is an action initiated by the control panel to cause something to happen such as initiating chemical feed, stopping chemical feed, initiating a neutralization cycle and the like.

As used herein, the term “free chlorine” is used with reference to a chlorine source that hydrolyses in the aqueous system to produce at least some portion of hypochlorous acid and hypochlorite ions. Examples include sodium hypochlorite, calcium hypochlorite, dichloroisocyanuric acid, trichloroisocyanuric acid, lithium hypochlorite as well as electrolysis devices the convert chloride ions to free chlorine in water.

As used herein, the term “free bromine” is used with reference to the formation or presence of hypobromous acid and possibly some portion of hypobromite ions.

As used herein, the term “oxidizer” is used to describe a chemical capable of oxidizing bromide ions to form free bromine and/or chloride ions to free chlorine. The oxidizer can comprise bromide ions and/or free bromine. The oxidizer can be a sanitizer exemplified by calcium hypochlorite, sodium hypochlorite, lithium hypochlorite and the like. One non-limiting example of an oxidizer comprising bromide ion donor is TowerBrom® 90M sold by Occidental Chemical Corporation. Other non-limiting examples of oxidizers include potassium monopersulfate, trichloroisocyanurate, dichloroisocyanurate, 1-Bromo-3-chloro-5,5-dimethylhydantoin and the like. Electrolysis of chloride ions to produce free chlorine is also a suitable oxidizer.

As used herein, the term “inactivation” is used with reference to the ability to deactivate, kill, or destroy microbiological organisms.

As used herein, the term “microbiological organisms” is used with reference to all forms of microbiological life forms including: parasites, bacteria, viruses, algae, fungus, and organisms encased in biofilms.

As used herein, the term “free halogen donor” is used with reference to a halogen source which acts as an active oxidizer when dissolved in water. Chlorine based free halogen donors form at least one of Cl₂, HOCl, and OCl⁻ (also referred to as free chlorine) when added to water, whereby the species formed is pH dependent. Bromine based free halogen donors form at least one of Br₂, HOBr, and OBr⁻ (also referred to as free bromine), again the species being pH dependent.

As used herein, “sensor for controlling the feed of sanitizer” is used with reference to ORP and/or amperometric sensors that are in fluid contact with the water of an aquatic facility, and provide measurements used for controlling the feed of a sanitizer (e.g. chlorine and/or bromine). While only one sensor is used to control the sanitizer at any given time, it is beneficial to monitor both ORP and free chlorine. Also it may be advantageous to be able to switch between sensors depending on the method of remediation being employed. For example, daily remediation may best be controlled using an amperometric sensor for controlling the sanitizer to limit the concentration of sanitizer in the water. This ensures the pool can be readily opened without the need for removing excess sanitizer before opening. However, during a rapid recovery shock, it may be advantageous to increase the sanitizer concentration to accelerate the cyclic process when in-situ generation of chlorine dioxide is used. The ability to program the programmable controller to switch between sensors based on the method being used can be very beneficial.

As used herein, “amperometric sensor” 10 describes a device that is in fluid contact with the water of an aquatic facility and is used to measure the concentration of sanitizer exemplified by free chlorine. The amperometric sensor 10 can be used to control the feed of sanitizer.

As used herein, “chlorine dioxide sensor” 14 describes a device that is in fluid contact with the water 4 of an aquatic facility and is used to measure the chlorine dioxide concentrated used to remediate the aquatic facility. Generally the chlorine dioxide sensor 14 is an amperometric sensor that incorporates a gas permeable membrane that allows chlorine dioxide gas to permeate the membrane while isolating the sensor from water soluble oxidizers like chlorine. The chlorine dioxide sensor 14 can be any suitable sensor that can be used to selectively measure the chlorine dioxide. One example of another type of chlorine dioxide sensor is a colorimetric device that utilizes lissamine green reagents to selectively measure chlorine dioxide in the presence of sanitizers.

As used herein, “ORP sensor” 8 describes a device that is in fluid contact with the water of an aquatic facility and is used to measure the Oxidation Reduction Potential (ORP) of the water 4. ORP sensor 8 can be sued to control the feed of sanitizer.

As used herein, “chemical feed systems” 40 describes in broad terms any desirable means for applying chemicals to the water 4 of an aquatic facility. Non-limiting examples of chemical feed systems include: chemical metering pumps, educators, erosion feeders such as a chlorinator or brominator.

As used herein, “Heterotrophic plate count (HPC) is also known by a number of other names, including standard plate count, total plate count, total viable count or aerobic quality count. It does not differentiate between the types of bacteria present nor does it indicate the total number of bacteria present in the water—only those capable of forming visible colonies under specified conditions on certain non-selective microbiological media. Varying the incubation temperature will favour the growth of different groups of bacteria. As it gives more meaningful information about pathogenic (disease-causing) bacteria, 35° C. (or 37° C.) is the preferred incubation temperature. HPC does not necessarily indicate microbiological safety as the bacteria isolated may not have been faecally-derived but it does give a measure of the overall general quality of the pool water, and whether the filtration and disinfection systems are operating satisfactorily. Results reported by the laboratory are traditionally expressed as colony forming units per millilitre (CFU/mL) which equates to the number of bacteria in each millilitre of the original sample of water. A HPC count of less than 1 CFU/mL indicates that the disinfection system is effective. If the count is between 10 and 100 CFU/mL, a routine investigation should be conducted as soon as possible to ensure that all the management operations are functioning properly.

As used herein, “CFU” (Colony Forming Units) is a unit used in microbiology to estimate the number of viable bacteria or fungal cells in a sample.

In order to support the cyclic process, bromide ions can be applied to the water separately and/or during the remediation cycle. If a bromide donor (i.e. sodium bromide) is applied separately it can be advantageous to include a tracer to track the concentration of bromide ions. One preferred tracer is a molybdate donor such as sodium molybdate. Regardless of the source of bromide donor or its method of application to the water, its presence during the remediation cycle significantly increases the efficiency of the chlorine dioxide generation within the conduit as well as driving the cyclic process in the pool water to achieve the desired Ct value.

Once the target Ct value is achieved the remediation cycle can be terminated. The programmable controller can be programmed to automatically feed a reducing agent to the water based on the excess residual chlorine dioxide, oxidizer and/or sanitizer in the water. The approximate concentrations of said residuals can be determined by either direct measurements utilizing amperometric and chlorine dioxide sensors and/or by calculation.

Calculated residuals can be determined by knowing the relative amounts of chlorite ions and oxidizer/sanitizer applied to the swimming pool. Knowing the relative amounts of each said chemical allows for approximating the amount of reducing agent needed to neutralize the excess residuals and accelerate the process of achieving compliance with the Dept of Health regulations to reopen the pool for use.

Algorithms can be programmed into the programmable controller for achieving compliance with the Dept of Health regulations for swimming pool water quality. Once the sensors detect the swimming pool water is within the compliance, programmable controller can notify the appropriate personnel that the pool is ready for use by patrons. Controller display can signal the pool is ready for opening and/or remote communications can notify managers via a call or an app to their phones or computers.

EXAMPLES

A 46,000 gallon swimming pool in Boca Rotan Fla. was used as a test site for testing automated control of remediation cycles. Daily remediation using the cyclic process was performed in the evening hours, while Rapid Recovery Shock using both the cyclic process and UV activation of chlorite ions was performed during daylight hours.

The swimming pool was equipped with a System 5 controller acquired from BECS Technology, Inc. located in Saint Louis, Mo. The System 5 controller comprised ORP, pH, amperometric and temperature sensors. A CRONOS chlorine dioxide controller was acquired from Process Instruments located in Lancashire, UK. The CRONOS controller was fitted with a DioSense sensor comprising an amperometric sensor capped with a gas permeable membrane. The CRONOS was calibrated using a lissamine green test that is specific to chlorine dioxide. Both control systems have data logging and the System 5 controller further comprised events logging capability to record time and duration of chemical feed etc.

A side stream of water circulated through the filter system was used as source of water for the described sensors. After passing thru the sensor's flow cells, the water was discharged into the diatomaceous earth filter pit.

Calcium hypochlorite was the sanitizer and hydrochloric acid was used for pH control. Cryptolyte® is a trademarked source of 25% active sodium chlorite solution. The pool water was treated with granular sodium bromide to provide approximately 15 ppm bromide ions (Br).

Test #1 is represented by FIGS. 1 and 2. Test #1 consisted of a daily remediation using the cyclic process. The sanitizer feed was controlled by ORP. The remediation cycle was initiated automatically at 8:00 pm by the System 5 controller. Cryptolyte® was applied at a dosage of 0.2 lbs per 10,000 gallons of pool water (approximately 0.44 ppm as ClO₂ ⁻). FIG. 1 shows the chlorine dioxide concentration measured by the CRONOS controller. The corresponding Ct values are indicated. FIG. 2 illustrates the events log for Test #1. The events log shows Crytpolyte was applied beginning at 8:00 μm and the event lasted for 15 minutes. The ORP dropped significantly due to the application of sodium chlorite which is a source of demand. The drop in ORP caused the System 5 controller to begin feeding sanitizer to regain the ORP set-point. A Ct value of 66 (min×mg/l) was achieved in 5 hours which based on GLP data illustrated in FIG. 8 is sufficient to achieve a 3-log reduction in Cryptosporidium.

Test #2 is represented by FIGS. 3 and 4. The process of Test #1 was repeated with the exception the calcium hypochlorite feeder was bypassed to prevent the spike in chlorine concentration thereby representing amperometric control of the sanitizer. While the amperometric measurement showed virtually no change in free chlorine, the cyclic process allowed for the remediation cycle to achieve a Ct value of 76 (min×mg/l) by 3:00 am.

Test #3 represented by FIGS. 5 and 6 illustrates a rapid recovery shock using a combination of the cyclic process and UV activation of chlorite ions. The pool water was treated with 0.5 ppm of a chromophore comprising Keyfluor™ White CBS-X which possesses a UV absorbance peak near 360 nm but only minimal UV absorbance at 260 nm. This allows the UV from the sun to activate chlorite at 260 nm but block the decomposition of chlorine dioxide with a UV peak at 360 nm. The remediation cycle was initiated at 9:15 am (FIG. 6). Cryptolyte was applied at a dose of 0.4 lbs per 10,000 gallons of pool water providing approximately 0.88 ppm as ClO₂ ⁻.

FIG. 5 illustrates a Ct value of 64 (min×mg/l) was achieve at 11:20 am just over 2 hours and five minutes after initiation of the remediation cycle.

A 15 ml sample of water was taken from 1250 ml beaker of water and treated with 0.3 ml of 0.5 wt % NaOCl, 0.2 ml of 1.25 wt % NaClO₂ and 0.2 ml of 1.6 wt % HCl all reported as active and was allowed to reacts for 60 seconds to replicate a low dosage evening remediation cycle. After 60 seconds of reaction time the sample was decanted into the beaker of stock water and allowed to mix for 60 seconds. Chlorine dioxide was measured using a Palintest Kemio test kit for chlorine dioxide. The beaker sample measured 1.34 ppm as ClO₂ correlating to a 90% conversion of chlorite to chlorine dioxide.

A 95 ml sample of water was taken from 1250 ml beaker of water and treated with 1.32 ml of 0.5 wt % NaOCl, 1.2 ml of 1.25 wt % NaClO₂ and 1.2 ml of 1.6 wt % HCl all reported as active and was allowed to reacts for 60 seconds to replicate a shock treatment. After 60 seconds of reaction time the sample was decanted into the beaker of stock water and allowed to mix for 60 seconds. Chlorine dioxide was measured using a Palintest Kemio test kit for chlorine dioxide. The beaker sample measured 8.62 ppm as ClO₂ correlating to a 97% conversion of chlorite to chlorine dioxide.

It is to be understood that the foregoing illustrative embodiments have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the invention. Words used herein are words of description and illustration, rather than words of limitation. In addition, the advantages and objectives described herein may not be realized by each and every embodiment practicing the present invention. Further, although the invention has been described herein with reference to particular structure, steps and/or embodiments, the invention is not intended to be limited to the particulars disclosed herein. Rather, the invention extends to all functionally equivalent structures, processes and uses, such as are within the scope of the appended claims. Those skilled in the art, having the benefit of the teachings of this specification, may affect numerous modifications thereto and changes may be made without departing from the scope and spirit of the invention. 

1. A method for accelerating remediation of a main body of water in an aquatic facility, the method comprising: calculating a Ct value of the water by a programmable controller; activating chemical feed systems by the programmable controller so that the chemical feed systems deliver an acid, an oxidizer and a chlorite ion donor to a conduit connected to the water; allowing the acid, the oxidizer and chlorite ion donor to react in the conduit and form chlorine dioxide; and supplying the chlorine dioxide from the conduit to the water; and sustaining a concentration of chlorine dioxide in the water until a targeted Ct value of the water is reached to achieve remediation of the water.
 2. The method according to claim 1, further comprising measuring a chlorine dioxide concentration of the water by chlorine dioxide sensor in communication with the programmable controller; and recording the chlorine dioxide concentration and calculating a Ct value of the water by the programmable controller based on the chlorine dioxide concentration.
 3. The method according to claim 1, further comprising measuring a pH concentration of the water by a pH sensor in communication with the programmable controller; and controlling the pH concentration of the water by the programmable controller.
 4. The method according to claim 1, further comprising measuring a sanitizer concentration in the water by a sanitizer sensor in communication with the programmable controller; and controlling the sanitizer concentration in the water by the programmable controller.
 5. The method according to claim 1, wherein the programmable computer uses an algorithm to calculate the Ct value comprising: Ct value=[(|ΣX _(n))÷n]×T Where: “X” is the chlorine dioxide concentration in mg/l (or ppm); “n” is a number of chlorine dioxide values recorded over a period of time since beginning the remediation cycle; and “T” is the period of time (minutes) that has lapsed since beginning the remediation cycle.
 6. The method according to claim 1, further comprising calculating the Ct value based on a rolling average of the chlorine dioxide concentration in the water.
 7. The method according to claim 1, wherein the sanitizer sensor is an ORP sensor.
 8. The method according to claim 1, wherein the sanitizer sensor is an amperometric sensor.
 9. The method according to claim 1, wherein the sanitizer sensor is both ORP and amperometric sensors.
 10. The method according to claim 1, wherein implementation of the remediation cycle is initiated automatically by the programmable controller.
 11. The method according to claim 1, wherein the implementation of the remediation cycle is initiated manually.
 12. The method according to claim 1, wherein the programmable controller calculates, records, and stores the Ct value.
 13. The method according to claim 1, wherein the programmable controller displays the Ct value.
 14. The method according to claim 1, wherein the programmable controller terminates the remediation cycle.
 15. The method according to claim 14, further comprising providing a reducing agent feed system in communication with the programmable controller, and the programmable controller adding a reducing agent from the reducing agent feed system to neutralize excess chlorine dioxide and oxidizer in the water.
 16. The method in accordance with claim 1, wherein the oxidizer is a sanitizer.
 17. A system for controlling the accelerated remediation of water in an aquatic facility, the system comprising: at least one sanitizer sensor for measuring a concentration of sanitizer in the water; a pH sensor for measuring a pH of the water; a temperature sensor for measuring a temperature of the water; a chlorine dioxide sensor for measuring the concentration of chlorine dioxide in the water; chemical feed systems for supplying an acid, an oxidizer and a chlorite ion donor to a conduit in communication with the water; a programmable controller in communication with the sanitizer sensor, the pH sensor, the temperature sensor, the chlorine dioxide sensor, and the chemical feed systems; the programmable controller is programmed to implement an accelerated remediation cycle by activating the chemical feed systems to achieve localized high concentrations of the acid, the oxidizer and the chlorite ion donor which react to form chlorine dioxide in the conduit that is supplied to the water; the programmable controller is programmed to record a chlorine dioxide concentration measured by the chlorine dioxide sensor; the programmable controller is programmed to calculate a Ct value of the water; and the programmable controller is programmed to sustain a concentration of chlorine dioxide in the water until a targeted Ct value is reached to achieve remediation.
 18. The system according to claim 17, wherein the programmable controller is programmed to control a pH concentration of the water.
 19. The system according to claim 17, wherein the programmable computer is configured to control a concentration of sanitizer in the water.
 20. The system according to claim 17, wherein the programmable computer is configured to control the pH of the water in the conduit during the accelerated remediation cycle.
 21. The system according to claim 17, wherein the chemical feed system supplies reducer to the conduit, and the programmable controller is programmed to terminate the remediation cycle by activating the chemical feed systems to apply the reducing agent to the water to neutralize excess chlorine dioxide and sanitizer in the water. 